Fig. 2. Numerical simulations. (A) Three-dimensional schematic drawing of the segment of channel 4 used in the numeric simulations with a motionless sphere at the barrier. The mesh used in the simulations is shown by thin lines. (B) Two-dimensional cross-section of the channel in the xz-plane of symmetry (vertical midplane) with a freely moving sphere at (–30, 0, 30) µm from the rest position. Curved lines are the streamlines with the flow directed from left to right. Double-headed arrow shows the principal axis of tensile forces exerted at the sphere by the hydrodynamic stresses. Note the minimal bending of the streamlines in the vicinity of the sphere, as the sphere is moving together with the fluid.